Solar heater



June 11, 1968 H, E. THOMASQN SOLAR HEATER Filed Oct. 22, 1965 JpreadeMa-fvr'ia/ United States Patent 3,387,602 SOLAR HEATER Harry E.Thomason. District Heights, Md. (6802 Walker Mill Road SE., Washington,DC. 20027) Continuation-impart of application Ser. No. 46,213, July 29,1969, which is a continuation-in-part of application Ser. No. 151,320,Nov. 9, 1961. This application Oct.

22, 1965, Ser. No. 591,964

16 Claims. (Cl. 126-271) The present invention relates to an improvedsolar heat collector which is simple and low cost in construction,highly efiicient in operation and which has a long life.

This application is a continuation-in-part of my copending Patent No.3,254,643, for Solar Heat Apparatus, issued from application S.N.46,213, filed July 29, 1960, and

Patent No. 3,236,294, for Basementless Solar Home,

issued from application S.N. 151,320, filed Nov. 9, 1961.

In the drawing:

FIG. 1 is a cross sectional view through one form of the invention;

FIG. 2 is a cross sectional view through a modified form of theinvention;

FIG. 3 is a cross sectional view showing a detail of a furthermodification;

FIG. 4 is a modification of the fluid introducing and spreadingapparatus.

Solar energy rays 1 enter the collector through one or moresubstantially transparent covers. One such cover is illustrated at 2. Asolar heat collecting overlayment 5 has fluid spreader-heat collectormaterial 4 closely adjacent thereto and a second substantiallytransparent cover 3 spaced closely adjacent to material 4. Theoverlayment S, of glass fiber, asbestos, paper, wood, pulp, rag or thelike, is impregnated with a fluid, as asphalt, coal tar pitch or such. Asand-asphalt, sand-coal tar mixture, or such may be used under certainconditions. The surface turned toward the sun is preferably dark orblack and is capable of absorbing solar energy and converting it toheat. A barrier 6 and a base material 7 are preferably provided underoverlayment 5, the base being insulating in character. Barrier 6,aluminum foil for example, minimizes passage of oils or fluids out ofoverlayment 5 and entrance of oxidizing air into this overlayment.Members 8, 9 secure the parts in assembled relationship.

The present invention may be used to heat various fluids. Water, forexample, may be used as a fluid to transfer heat from the collector to apoint of use or storage. Cold water may be introduced by distributor 10to trickle and flow down between cover 3 and solar heat collectingoverlayment 5 through solar heat absorber-fluid spreader 4, down totrough 11. The solar heat absorber-fluid spreader 4 may be wire mesh,rigid, non-fluid granular material such as sand, or such. Liquidattracting or liquid repelling agents may be used on fluid spreader 4 ifdesired to help keep the liquid in channels as it descends along thewire mesh or granular material. These agents may be used in parallelstrips, ridges, or such, extending from top-to-bottom, to minimizeside-skewing of the liquid. It has been found that a wetting agent,added to water, assists in spreading water over black sand-coatedasphalt shingles as in FIG. 2, for example.

Underlayment base 7 may comprise, for example, wood sheeting 12, glassfiber or mineral wool 13 and aluminum heat reflective vapor barrier 14to minimize reversed heat passage back through the collector at night.Barrier 14 also prevents moisture from entering the collector, andcondensing on barrier 6.

In FIG. 3, instead of passing the heat transfer fluid to be heatedbetween. the overlayment 5 and transparency 3, as in FIG. 1, such fluidmay be passed over transparency "ice 3' between transparencies 3' and 2.Fluid flow channeling means, wetting agents or such may be used toobtain uniform wetting of transparency 3'. With this type ofconstruction and operation the fluid spreader material 4 may be used oreliminated as desired. It material 4 is eliminated, inner transparency 3may be placed directly in contact with overlayment 5, with no air orliquid passage space, to further reduce oxidation and loss of oils andfluids from the upper surface of the heat collecting overlayment.

The following discussion will lead to a better understanding of theprinciples involved and the value of the present combination of parts.

Numerous problems are encountered because of unusual conditions presentin solar heating systems. In a solar heat collector, temperatureextremes and temperature cycling deteriorate materials and much morerapidly than they would deteriorate under normal conditions. Asexamples, one researcher has written that screws used to hold collectorparts together were pulled loose during temperature cycling because thecollector expanded While collecting heat and contracted during the coolnighttime. Consequent pushing and pulling on the parts soon loosened thescrews. The chief scientist of a paint company advises that mostordinary paints would soon crack and peel off from metal solar heatcollector sheets due to high temperatures, and repeated temperaturecycling, with expansion and contraction of the paint at a rate differentfrom that of the collector sheet. One researcher reported shattering ofsubstantially all of the glass covering soon after his large solar heatcollectors for a househeating system were constructed. Another reportedthat window glazing compounds, which would last more than twenty yearsin ordinary building construction, dried and cracked within a few yearswhen used as solar heat collector glazing. Another report showed that atough plastic film which would last five years or longer as a greenhousecovering material would fail quicker when used as an inner glazingmaterial, protected by an outer glass covering, in a solar heatcollector.

Products containing oils, asphalt, tar or such would appear useful insolar heat collectors. They are black and solar heat absorptive incharacter. They are not as subject to corrosion as some materials. Theycan be used to preserve certain materials. They are plastic when appliedat moderate temperatures and are thereby capable of expanding andcontracting with temperature changes. However, such materials have notbeen found satisfactory for use as solar heat collector sheets or ascoatings for metal heat collector sheets. When the collector gets cold,asphalt or tar base coatings get hard, brittle, and tend to crack. Asthe collector gets hot the asphalt or tar base coatings tend to creepdown the inclined sheet and drip from or pile up at the bottom. As thecoatings age some of the oils oxidize and volatilize out leaving thecoatings increasingly drier, brittle and lifeless. The aging, oxidizing,drying process is accelerated by the high temperature baking in a solarheat collector, sometimes exceeding 250 degrees Fahrenheit.

in a preferred form of the present invention, a sheet of fibrousmaterial is impregnated with asphalt, tar, oils or other fluids to helppreserve the fibrous materials and keep them long-lived. The fibrousmaterial, in turn, helps keep the preservative fluids from creeping andcracking. Dilficulties arise, nevertheless, because the preservativefluids tend to oxidize, volatilize away and leave the fibrous materialdry, brittle and subject to cracking and deterioration. Also, suchsheets do not conduct heat readily, and tend to repel water. It isdifficult to get heat collecting water to flow evenly over, fullycontact, and collect the solar produced heat from such sheets. Thus, itwould seem that a disadvantage oflsets each advantage as we attempt touse products containing oils, asphalt, tar, etc.

The present invention discloses examples of certain combinations ofparts and materials which render such fluid containing fibrous materialsusable and long lived to collect solar heat and transfer it to aheat-transfer fluid, even in the extremely rough environmentalconditions in solar heat collectors which have shattered glass,deteriorated tough plastic films, ruined paints and glazing compoundsand torn screws from their anchorings.

Referring again to the drawing, if water is to be passed through thecollector from distributor It) to trough 11, and if the rigid orsemi-rigid base underlayment 7 comprises a material at 12, such asplywood for example, it should be protected from water, water vapor orsteam which is present between the transparency 3 and the solar heatcollecting overlayment 5. The overlayment itself preferably containsoils or other preservative softening fluids which render the overlaymentlong-lived and resistant to leakage of water, water vapor or steam.Vapor barrier 6 keeps oxidizing air from getting to overlayment S.Barrier 6 may also be resistant to water vapor, in which event it givesadded protection against water vapor damage to wood or such at 12. Inaddition, vapor barrier 6 should be resistant to oils, oil vapors andsuch coming from overlayment 5. Thus, barrier 6, which may be reflectivemetal foil, for example, minimizes oxidation in and escape of oils andvolatilizable fluids from overlayment 5. This minimizes drying out andcracking of the overlayment, thereby adding greatly to the life of theoverlayment.

High temperature baking and solar energy rays 1 accelerate oxidizationand drive off the oils and volatilizable fluids from the upper surfacealso of overlayment 5. Substantially transparent cover 3 is provided toadmit solar energy rays 1 and to minimize oxidization and escape of suchoils and fluids from the upper surface. This cover is preferably veryclosely spaced above the overlayment to minimize the amount of air,convection currents, etc. and drying eflfects thereof, between theoverlayment and trans parent cover. The close spacing between the coverand overlayment also helps keep the fluid spread evenly over the solarwarmed surfaces of the overlayment inside of the transparent cover.

The present invention departs from recommendations of the experts. Thetransparent cover 3 is placed in very close proximity to the overlaymentcollector sheet 5, instead of an inch or so above as is customary. Thisminimizes movement of the air and oxidization or drying of the collectorsheet. Fluid spreader material 4 also helps reduce air convectioncurrents. In the modification of FIG. 3 the transparency is preferablyin contact with the collector sheet, thereby substantially eliminatingcontact of the hot oxidizing drying air with the overlayment collectorsheet and prolonging the life of the overlayment.

A further benefit is realized from use of fluid spreader material 4,which is also a solar heat absorbing material. Such fluid spreader-heatcollector material provides shade for much of the surface of overlayment5 to thereby reduce the deteriorating effects of direct sunshine. Insome instances fluid does not flow perfectly and absolutely uniformlyover an entire solar heat collecting sheet or overlayment. A heatconducting mesh at 4 assures that the heat can flow through the meshfrom areas of heat collection but poor or no fluid flow, to areas ofgood fluid flow.

The inner transparency 3, of plastic, glass or other, may be clampedunder spreader-supports 8 if desired. The degree of tightness of theclamping of such spreader-support will squeeze the spreader material 4more or less tightly against or into overlayment 5. This results in anadjustable valve action whereby the degree of Spreading of the fluid maybe adjusted. If desired spreader-supports 8 may be supported directly byfluid spreader material 4, and transparency 3 may extend between onemember 8 and the next without extending beneath spreader supports 8.

In this type of construction also, members 8 serve to spread the fluidas it passes thereunder.

FIG. 4 illustrates that spreader-supports, as at 8, may be used for theinitial spreading of the liquid as it is brought onto the heat collectoroverlayment 5. Thus, instead of using a distributor pipe with holes init, as shown at the top of the collector in Patent Number 3,145,707, theliquid can be pumped onto the heat collecting overlayment directly, asat 18, in one or more main streams. The liquid, illustrated at 19, mustthen spread out into many small streams to pass under spreader-bar S.Thus, we can eliminate a part, as distributor pipe 10, in FIG. 1, andyet retain the function, thereby simplifying the apparatus and loweringconstruction costs. If desired, the spreader 8 may be inclined slightlyto aid in causing the fluid 19 to spread from the inlet pipe 18 towardthe side or sides of the collector.

The spreader-supports, in this combination, yield an additional veryimportant function in solar seat collectors which are vertical, or nearvertical. In a construction as in Patent No. 3,145,707, wherein the heatcollector sheet is corrugated, V-crimped, or similarly distorted, thehills-and-valleys become quite ineffective to channel the flow of liquidin parallel paths from top-to-bottom if the collector is stoodvertically on end. If a corrugated sheet is stood vertically on end,there are no hills-andvalleys, only ins-and-outs. Therefore, fluidchanneling ordinarily is not efiective.

The construction described herein makes it feasible to operate thecollector in a more nearly or completely vertical position and yetobtain good spreading characteristics of the fluid flow, and goodcontact between the fluid and the heat collecting overlayment, forreasons to follow. Cold liquid to be heated is introduced ontooverlayment 5 by distributor 10, or by spreadendistributor 8 asdescribed above. It clings to overlayment 5 and fluid spreader 4 bymolecular attraction as it descends. However, molecular attractionwithin the liquid itself also tends to gather the liquid into streams.If such streams form, they are sometimes deviated from their normaldownward path as they follow paths of least resistance, or of greatestmolecular attraction or repulsion. If these streams traveled 10, 20, 30,40, 50 feet or further down the collector overlayment, without beingre-spread, this could leave large areas of heat collecting overlaymentunvisitecl by the heat transfer liquid. However, the successivespreadebsupports 8 keep re-spreading and redistributing the liquid as itdescends the overlayment, thereby increasing contact between the liquidand the heat collecting materials at 4, 5, thereby increasing heatcollection ability of the collector.

Barrier 14 is preferably both reflective of heat, and resistant topassage of vapor. The solar heat collector may be used as a wall of anenclosed area such as a swimming pool, a home or other building, wherethe air inside is warmed and has fairly large quantities of water vaportherein. Infrared heat rays are reflected back into the enclosed area ifbarrier 14 is reflective. Also, moisture Within the area is preventedfrom entering the insulation 13 and condensing or i'Ieezing in theinsulation or on vapor varrier 6 during cold nights or at other periodswhen solar energy input is low and barrier 6 is cool.

FIG. 2 illustrates a modification. One or more transparent covers may beused. A rigid or semi-rigid insulating material, such as foamed glass,foamed plastic, or such, is used at 15.

FIG. 2 also illustrates a detail as to how the heat collectingoverlayment may be constructed. It has been found that, in solar heatcollectors, some forms of overlayment containing asphalt or tar or otheroil bearing or fluid containing materials, Will expand and contract andthereby buckle and stretch as temperatures fluctuate widely, and asliquids, vapors, and humidity conditions adjacent to the overlaymentfluctuate or are varied. This tends to shorten the life of theoverlayment material and to disrupt and unbalance the flow of fluid oversuch overlayment. The overlayment here comprises a series of smallsheets, preferably but not necessarily overlapped like shingles.Transparency 3, bearing directly on the overlayment, helps to overcomethese problems by keeping the overlayment flat. If the transparency isfairly heavy and the collector is inclined, or flat, the weight of thetransparency may be sufficient to keep the overlayment held firmly inplace and to hold the flow of fluid to thin proportions. If thetransparency is light in weight, or if the collector is mountedsubstantially vertically, spreadersupport members 8 may be used as inFIG. 1 to clamp the transparency closely adjacent to the overlayment,spaced by fluid-spreader material 4', which may be screen wire, asillustrated in FIG. 1, non-volatilizable granules, or such.

The overlayment may be constructed as follows to further minimize thetendency to buckle and stretch. An under-overlayment member 16 maycomprise one or more large sheets of material which have a minimum ofjoints per solar heat collector unit. If desired, these underoverlaymentsheets may contain oils or other fluids to keep them from deterioratingand to keep them pliable, expandable and compressible. They may beoverlapped or constructed as plies, with successive layers running atright angles to one another, or with wide overlaps of the plies, or withboth features. Then, an outer-overlayment member 17, of smaller piecesof material, may be added, and the entire assembly secured to the rigidinsulating base 15, or to a rigid underlayment as illustrated at 12 inFIG. 1 In such case a barrier may be added as at 6 in FIG. 1. andanother barrier may be used between mem bers 17 and 16. Such barriersmay be aluminum foil, for example, which are simple and inexpensive andgive further protection against transfer of water, steam, vapor or heatfrom heat-collecting overlayment 17 to the rigid underlayment 12(FIG. 1) or (FIG. 2).

Referring again to FIG. 3, overlayment 5 has a substantially transparentcovering 3', preferably directly in contact with the upper surface ofthe overlayment. Thus, ambient air is precluded from coming into contactwith the upper surface of the overlayment and oxidation andvolatilization of the fluids in the overlayment are held to a minimum.Solar produced heat generated at the overlayment may be removed in oneor more ways. As examples, the heat from the overlayment may beconducted to barrier 6 and picked up by a heat transfer fluid contactingthe barrier. Alternatively, the heat from the overlayment may beconducted to transparency 3' (which also converts a portion of the solarenergy into heat due to impurities in the transparency). The heat may bepicked up by a heat transfer fluid contacting this transparency. One ormore outer transparencies, as at 2, may be used adjacent to transparency3 with heat transfer fluid being passed between transparency 3' and suchouter transparency.

The present invention represents a further step forward in simplifyinglarge solar heat collector construction and in cutting the cost. In thelow temperature range especial- 1y, as used for some solar home heatingsystems, domestic water heating, swimming pool heating and such, thepresent invention is highly efficient in collecting solar heat.

What I claim is:

1. Solar heat collecting apparatus comprising: an insulting baseunderlayment; an overlayment of solar heat collecting material having anupper solar heat collecting surface, said overlayment comprising arelatively stable material containing a fluid, a portion of whichoxidizes or volatilizes when exposed to heat or atmospheric conditionsor both; a substantially transparent, substantially liquid-tight andsubstantially vapor-tight covering material closely adjacent to saidoverlayment to admit solar energy and to minimize oxidation andvolatilization from the upper surface of said overlayment; means tointroduce a heat transfer fluid to be heated to the space between saidoverlayment and said covering material; means between said overlaymentand said covering material to spread said heat transfer fluid as itflows through said collector; and means to collect the heated fluidafter it has passed through said collector for return to a point of useor storage.

2. Solar heat collecting apparatus as in claim 1 and a barrier betweensaid underlayment and said overlaymerit and said barrier betweensubstantially vaportight to minimize oxidation and volatilization fromsaid overlayment to or through said underlayment.

3. Solar heat collecting apparatus as in claim 2 wherein said heattransfer fluid is a vaporizable liquid and wherein said covering servesthe additional function of minimizing vaporization of heat transferfluid upwardly and said barrier serves the additional function ofminimizing leakage or vaporization of heat transfer fluid downwardly.

4. Solar heat collecting apparatus as in claim 1 wherein said meansbetween said covering material and said overlayment comprises amesh-like heat conducting material which helps conduct and distributeheat within the apparatus and which receives and absorbs solarradiations and converts such into heat.

5. Solar heat collecting apparatus as in claim 1 wherein said meansbetween said covering material and said overlayment comprises anon-vaporizing granular material with surfaces which receive and absorbsolar energy and convert such into heat.

6. Solar heat collecting apparatus comprising: an insulating baseunderlayment comprising sheeting material, such as wood, which would beadversely affected by water or water vapor; an overlayment of solar heatcollecting material having an upper solar heat collecting surface, saidoverlayment comprising a non-rigid material containing a fluid whichhelps preserve and keep the material nonrigid but which tends to oxidizeand volatilize when subjected to atmospheric conditions, or high solarheat collector temperatures, or both; vapor resistant reflectiveinsulating material between said base underlayment and said overlaymentto reduce vapor damage to said underlayment and heat lossestherethrough; a substantially transparent vapor resistant coveringmaterial closely adjacent to said overlayment to minimize oxidation andvolatilization from the upper surface of said overlayment and to admitsolar energy to said overlayment while reducing heat radiations fromsaid overlayment; means to introduce a heat transfer fluid to be heatedto the space between said overlayment and said covering material; meansbetween said overlayment and said covering material to spread said heattransfer fluid as it flows through said collector; means to collect theheated fluid after it has passed through said collector for return to apoint of use or storage.

7. Solar heat collecting apparatus as in claim 6 and additional means tospread, and re-spread, said heat transfer fluid as it passes throughsaid apparatus.

8. Solar heat collecting apparatus as in claim 6 wherein saidunderlayment additionally comprises glass fiber or mineral fiberinsulation with a reflective foil surface turned toward and to reflectradiant heat emanating from said overlayment and said underlayment backtoward such overlayment and said underlayment.

9. Solar heat collecting apparatus as in claim 8 wherein said insulationincludes a vapor barrier with a heat reflective surface turned away fromsaid overlayment and said underlayment to reduce reversal of heat travelthrough said solar collector, and to reduce entrance of moisture intosaid glass or mineral fiber thereby reducing condensation or icing onthe reflective foil during periods of low solar heat input, such as atnight.

10. Solar heat collecting apparatus comprising: a base for supportingelements of said collector and providing insulation means to minimizeescape of heat through said base; a solar heat collecting overlaymentsupported by said base, said overlayment comprising non-rigid materialcontaining oxidizable or volatilizable fluids which help keep thematerial non-rigid, non-hard and non-brittle and capable of expandingand contracting with temperature fluctuations, humidity fluctuations andsuch, said overlayment having a solar heat absorbing surface turned awayfrom said base and toward incoming solar radiations; a substantiallytransparent member substantially parallel with said overlayment and inclose proximity thereto to admit solar radiations and to minimizeoxidation and volatilization of fluids from said overlayment; means toremove solar produced heat from said apparatus for transfer to a pointof use or storage; and solar heat collectingfluid spreader materialbetween said substantially transparent member and said overlayment.

11. Apparatus as in claim 10 wherein said solar heat collecting-fluidspreader material comprises heat conducting mesh having solar heatabsorbing surfaces, said mesh serving to collect solar energy, to reduceconvection currents between the overlayment and transparent cover, toreduce oxidization and volatilization from said overlayment, todistribute and conduct heat within the collector, and serving todistribute and channel heat transfer fluid passing through the heatcollecting apparatus.

12. Apparatus as in claim 10 wherein said solar heat collecting-fluidspreader material comprises non-volatilize.- ble granular materialhaving solar heat absorbing surfaces, said granular material serving tocollect solar energy, to reduce convection currents between theoverlayment and transparent cover, to reduce oxidization andvolatilization from said overlayment, and serving to distribute andspread heat transfer fluid passing through the heat collectingapparatus.

13. Apparatus as in claim 10 wherein said base comprises rigid orsemi-rigid foam insulation.

14. Apparatus as in claim 10 wherein said base comprises fluifyinsulation material such as glass fiber or mineral wool; a vapor barrierbetween said insulation material and said overlayment to minimizepassage of fluids into said insulation and to minimize escape of fluidsfrom or oxidization of said overlayment fluids.

15. Apparatus as in claim 10 and a second substantially transparentmember spaced from said first transparent member; spreader-supportsbetween said transparent members to keep re-spreading andre-distributing fluid as it flows over and receives heat from said solarheat collecting overlayment.

16. Means for introducing, distributing and spreading fluid into a solarheat collector comprising: a solar heat collecting sheet; fluid spreadermaterial adjacent to the upper surface of said heat collecting sheet; afluid spreader member extending substantially horizontally across saidheat collecting sheet and spaced closely adjacent to said heatcollecting sheet; and means to introduce fluid to be heated to saidsolar heat collector so that the fluid will spread out along said fluidspreader member, as restricted by said member, and will pass therebythrough said fluidspreader material.

References Cited UNITED STATES PATENTS 2,427,262 9/ 1947 Delano.3,102,532 9/1963 Shoemaker 126-270 3,146,774 9/1964 Yellott l262713,194,228 7/ 1965 Bargues 126-271 FOREIGN PATENTS 763,867 2/ 1934France. 840,926 1/ 1939 France.

CHARLES I. MYHRE, Primary Examiner.

1. SOLAR HEAT COLLECTING APPARATUS COMPRISING: AN INSULTING BASEUNDERLAYMENT; AN OVERLAYMENT OF SOLAR HEAT COLLECTING MATERIAL HAVING ANUPPER SOLAR HEAT COLLECTING SURFACE, SAID OVERLAYMENT COMPRISING ARELATIVELY STABLE MATERIAL CONTAINING A FLUID, A PORTION OF WHICHOXIDIZES OR VOLATILIZES WHEN EXPOSED TO HEAT OR ATMOSPHERIC CONDITIONSOR BOTH; A SUBSTANTIALLY TRANSPARENT, SUBSTANTIALLY LIQUID-TIGHT ANDSUBSTANTIALLY VAPOR-TIGHT COVERING MATERIAL CLOSELY ADJACENT TO SAIDOVERLAYMENT TO ADMIT SOLAR ENERGY AND TO MINIMIZE OXIDATION ANDVOLATILIZATION FROM THE UPPER SURFACE OF SAID OVERLAYMENT; MEANS TOINTRODUCE A HEAT TRANSFER FLUID TO BE HEATED TO THE SPACE BETWEEN SAIDOVERLAYMENT AND SAID COVERING MATERIAL; MEANS BETWEEN SAID OVERLAYMENTAND SAID COVERING MATERIAL TO SPREAD SAID HEAT TRANSFER FLUID AS ITFLOWS THROUGH SAID COLLECTOR; AND MEANS TO COLLECT THE HEATED FLUIDAFTER IT HAS PASSED THROUGH SAID COLLECTOR FOR RETURN TO A POINT OF USEOR STORAGE.